178 NERVOUS SYSTEM. 



In what is known to physiologists as muscular effort, the 

 mechanism of which has been discussed in another volume, 1 

 the glottis is closed, the thorax is fixed after a full inspira- 

 tion, and respiration is arrested so long as the effort, if it be 

 not too prolonged, is continued. The same synchronism, 

 therefore, obtains in this as in prolonged vocal efforts. In 

 experiments in which the muscular branch only has been 

 divided, shortness of breath, after violent muscular effort, is 

 observed; and this is probably due to the want of syn- 

 chronous action of the sterno-cleido-mastoid and trapezius. 

 The irregularity in the movements of progression in 

 animals, in which either both branches or the muscular 

 branches alone have been divided, is due to anatomical 

 peculiarities. Bernard has observed these irregularities in 

 the dog and the horse, but they are not so well marked in 

 the cat. There have been no opportunities for illustrating 

 these points in the human subject. 



Sublingual) or Hypoglossal Nerve (NiniK). 



The last of the motor cranial nerves is the sublingual ; 

 and its functions are intimately connected with the physi- 

 ology of the tongue in deglutition and articulation, though 

 it is also distributed to certain of the muscles of the neck. 



Physiological Anatomy. The apparent origin of the sub- 

 lingual is from the medulla oblongata, in the groove between 

 the olivary body and the anterior pyramid, on the line of the 

 anterior roots of the spinal nerves. At this point, its root is 

 lormed of from ten to twelve filaments, which extend from, 

 the inferior portion of the olivary body to about the junction 

 of the upper with the middle third. These filaments of 

 origin are separated into two groups, superior and inferior. 

 From this apparent origin, the filaments have been traced 



memoir of Bernard on the spinal accessory, in which the function of the ex- 

 ternal branch in the lower animals has been fully investigated by experiments. 

 1 See vol. Hi., Movements, p. 477. 



